Association Analysis Of Wheat Genetic Diversity And Grain Traits With SSR Markers

Synthetic hexaploid wheat(SHWs)is a new type of hexaploid wheat,which is an important material to study the genetic variation in the process of wheat evolution.It can be used for the exploration of the excellent resources of wheat close relatives,for further expanding the wheat genetic gene library,and the identification of the excellent genes.In this study,a population that consists of 86 synthetic wheat lines and 24 conventional wheat cultivars were constructed.We measured several grain traits,including the grain length,grain width,grain thickness and grain weight in Yangling(E1,E2),Sanyuan(E3)and Nanyang(E4)in 2015 and 2016 respectively.Then a cluster analysis was made for its genetic diversity and population structure analysis,by using 365 SSR markers which belong to the whole genome of wheat for its genome-wide scanning.Finally,we combined molecular markers and phenotypic traits for association analysis to identify more excellent alleles.The results are as followed:1.The statistic analysis results showed that both Yangling(2015)(E1)and Nanyang(2016)(E4)had the largest variation coefficient of 1000-grain weight and the smallest coefficient variation of grain thickness of synthesized hexaploid wheat.The differences of five phenotypic traits among synthesized hexaploid wheat were all extremely significant(P<0.001)in all environment,which indicated its wide differences and abundant diversity.2.365 polymorphic SSR markers were selected for genome-wide scanning in 110 test materials,2187 alleles were detected,and the average allele variation was 5.9918.The range of gene diversity was from 0.1944 to 0.8612,and the mean was 0.7247.The polymorphic information content of each primer(PIC values)was from 0.1755 to 0.8452,and the mean was 0.6848.The maximum and minimum values of gene diversity and PIC were the primers gdm99 and xgwm320,respectively.The highest of alleles variation number was in the D genome(1009),and the lowest was in the A genome(534);the gene diversity and PIC were the highest in the D genome and the lowest in the A genome.These results showed that the genetic diversity of D genome in synthetic wheat was relatively higher.3.The tested groups were divided into seven subpopulations,Synthetic hexaploid wheats were divided into five subpopulations,and conventional wheats were divided into two subpopulations.The result showed that there was a significant difference in genetic background between SHWs and conventional wheats.4.There is one significant marker associated with grain length and grain thickness respectively that can be detected under all environments;there is one significant marker associated with grain thickness that can be detected in only three environments;there are ten significant association markers that can be detected in only two environments.These significant markers provide basis for further excavation of superior alleles and wheat molecular marker assisted breeding.